2. If the Member Resource was created successfully, the server
responds with a status code of 201 and a Location header that
contains the IRI of the newly created Entry Resource. Media
Resources could have also been created and their IRIs can be
found through the Entry Resource. See Section 9.6 for more
details.

It should say:

2. If the Member Resource was created successfully, the server
responds with a status code of 201 and a Location header that
contains the URI of the newly created Entry Resource. Media
Resources could have also been created and their IRIs can be
found through the Entry Resource. See Section 9.6 for more
details.

Notes:

The Location header (as defined in HTTP/1.1) contains a URI, not a IRI.

I believe the schema unintentionally prohibits atom:link from being included in the categories document. Given that in another schema in the same appendix it is allowed, and going by the text in the normative sections, I believe this must be a cut and paste error.